Electrical trigger circuits



July 22, 1952 M. c. BUR-NS 2,604,589

ELECTRICAL TRIGGER CIRCUITS Filed May 15, I950 7-I:L: 9w 5- 5 SOURCE OF AI UTILIZATION TRIPPING W CIRCUIT ,IIvIPuLsEs I 6 /0 souRI-z 0F EXGITATION FREQl JENOY F LIE .J

SOURCE OF UTILIZATION TRIPPING ,IMPULSES I SOURCE OF EXOITATION FREQUENCY,

INvIzNToR fiery/Q Burns Patented July 22, 1952 uNrrEosTArEs PATENT, orrlcs' Meryl 0. Burns; .Richmond calitl, assignor to Mai-chant Calculating Machine Company, a corporation of California Application May-1'5, 1950, Serial No. 162,127

This invention"relates" to trigger circuits and" otherfsimilar circuits, and also concerns the utilization, in such circuits, of gas tubes whose characteristics are stabilizedby external means.

The use in such circuits of small, inexpensive gas tubes, such'as "the simple neon diode glow tube, has heretofore been inhibited by the inherent lack of stable and uniform characteristics of suchtubes.

It is therefore a principal object of the present invention to stabilize the characteristics -of-ga's tubes by an"'externa1ly applied excitation field.

Another 'object of the invention'is {to increase the uniformity in characteristics between any number of similar gas tubes by such excitation field fl "INT Q .1"

Anothen-and more specific objector the invention is to increase stability and/or uniformity in the cl i-aracteri'stics of'gastubes by excitation of such tubes with an externally applied audio or higher frequency field. F 1

A further object of the invention is to reduce the size 'and/orcost'of trigger circuits, or other similar circuits, by utilizing such uniformly stabilizecl'gas tubes in such circuits.

Another object of the invention is to fire and. extinguish thegas tubes of trigger circuits and the like by means of only the two principal electrodes of such tubes. k

The present invention is therefore basedupon the principle of applying an external excitation field to each of one or more gas tubes in a circuit to increase stability of the characteristics of each" tube and uniformity of'oper'ation' of'a plurality of such tubes. "While gas diodes and triodes are disclosed herein to illustrate thepresent invention,flthe fapplication'fof the above principle to other'types of gas filled tubes also increases their stabilityand uniformity in the same manner.

"'Otherlcbje'c'ts and applications of the invention will appearfr'om thefollowing description, with reference to the arawmgmwmch':

Figf l is "a schematic circuitdiagrani are pre ier'red embodiment of a trigger circuit; empm mg twogas i ifid' i q Fig. 2.1; a schematicci'rcuit diagram of a modifled embodiment ofa trigger circuit, employing tWQ a t riQ gsi I I It has heretofc're been necessary, in trigger circuits 'and other "circuits of asimilarnature, 'to usetube's' of inherently stable characteristics inorder'to achieve reliable operation. By application of the principles of the present invention, less stable tubes w'hichfar'e smaller and'less ex pensive" than those customarily usedymaype 6 Claims. (Cl. 25027) employedin such circuits. 'Ihis makespossible" a'reduction in the size and cost of the circuit: both through simplification of the circuit and through reduction in size and cost of the tubes. Referring-to Fig. 1', a pair of similar gas diodes I and 2 are connected in parallel between ground and the positive termina1 of a source"? of unidirectional potential, shown as a battery... The negative terminalof source '3 is groundedz' A resistor 4 is'connected in series in the'dis'cha'rge circuit of tube I; 'likewise,"a"resistor 5 'is"'icon'- nected in series in the discharge circuit of tube-I: Resistors 4 and 5 are of substantially equal'value," making the discharge circuits of tubes lt'an'dil symmetrical; 'The respective values of"the' -B'.-'I-"' voltage of source 3'and the 'breakdownpotentialsof tubes I and 2 are suchthat neither'tube' will be'discharged' solely by the 3+ potential pressed thereon. A source 6 of positive tripping: or firing pulses is connected in'paralle'lTto' the high potential'side of each tube I and? through a respective input condenser I and'8 of substan-r tiall'ycqual capacitance. A coupling condenser 9 connects the high potential sides of the two-1 tubes. The high potential electrodes of tubes ,I, and 2 will hereinafter be" designated as the plates of the respective tubes. M Operatic n. as a trigger circuit a In the normalconditionof. rest, neither Loft ej tubes I a'ndl isin a, firing condition, andwheii operation of the circuit is tobe .initiatedffroin; thisconditi'on, a positive. firing impulsellf source 6,. of sufficient magnitude when adde' B+- voltage to fire either tube, isimpressed L-i multaneousl'y. upon both tubes. Due tothefin' herent differences-between any two such tubes; their breakdown potentials will beat slightly dif; ferent levels. Therefore, the tube with uthe'low breakdown potential will discharge before b down potential is reached by the'jotlier tube. j I purposes of illustration,.it will bejassumedthat tube I has the lower breakdown potential discharged first.

Although the tripping pulse is fed to both tubes simultaneously, the circuit is so arranged that the tube which fires first 'producesia' negative impulse which is fed to the" other tube,'preventing that other tube from firing." 7 I' 5 When tube I fires, thepositive firing pulse fed from source Bis discharged'through that'tube-to ground. "The discharge currentfthrough tube-"I" and-resistor 4 causes a potential drop across'that; resistor," lowering the; plate potential'o'f tube I to" itspperaungqeva. 'The upcrating" level' 1s tinction or ionization level.

The plate potential drop of tube I, caused by the firing or" that tube, is fed through the coupling condenser 9 to tube 2, lowering the plate potential of tube 2 and preventing that tube from being fired by the tripping pulse. Thus, the firing impulse causes the plate potential of tube 2 to first surge upward almost to its breakdown level; second, the negative surge from the plate of tube I prevents tube 2 from reaching break-- down, and causes its plate potential to drop below B+ level to the operating level of tube I third, source 3 returns the plate potential of tube 2 to 3+ level through resistor 5. It is obvious that tube 2 does not fire during this: first phase of operation.

After the first tube fires (tube I in the present example), a stable condition is reached in which tube I is maintained at its operating level and tube12 at the somewhat higher B+ level. This stable. condition will prevail until tubes I and 2 receive the next tripping pulse from source 5.

Since tube I is already firing when it receives the second tripping impulse, its plate potential will not drop at that time, as it did after being fired by the first tripping impulse. Therefore, when such impulse is impressed upon tube ,2, that tube is raised above its breakdown potential and fired, since no negative surge from tube I across condenser 9 will interfere. As tube 2 fires the firing pulse from source 6 is discharged through that'tube to ground. The discharge current through tube 2: and resistor causes a potential drop across that resistor and a consequent drop of the plate potential of tube 2. drop is fed through the coupling condenser 9. to the plate of tube I, extinguishing that tub ir 1'the following manner.

It will be. rememberedthat, prior to the receipt of the second firing pulse, the plate of tube. I was atoperating potential. and tube 2 at 13+ potential. Since the second firing pulse raises both tube plate. levels by the same amount, tube I, at the peak of that pulse, will still be at a lower level than tube 2. When tube 2 fires and its plate drops to operating level, the plate potential of tube I drops by the same amount because of the negative surge from tube 2 to tube I across condenser 9. Tube I, in dropping the same amount as tube 2, falls to a lower value than does tube 2, because tube I started dropping from a lower level. Therefore, since tube 2 drops to its operating level, tube I drops somewhat below that level. The circuit values are so arranged that tube I drops to or below its ionization level and is extinguished, thereafter being raised to 13+ by source 3.

7 Receipt of each subsequent successive tripping impulse from source 6 causes conduction to shift from, one tube to the other in the manner de scribed above.

Tube stabilization Small inexpensive gas-filled tubes may be employed in the above-described trigger circuit, providing the operational characteristics of these tubes are stabilized in some manner. It has been found that such stabilization may be accomplished by an external means for causing excitation of the gas in such tubes with an audio or higher frequency field. The resulting stabilization is thought to be due to the establishing of well as positive tripping pulses.

an artificial degree of ionization of the gas in a tube which tends to eliminate diiferences in characteristics, both as between any two similar tubes and. as over a period of time in a single tube.

In Fig. 1, such stabilizing field is shown as being supplied by a source II of the excitation frequency. A receptive external electrode I2, associated with each tube, is connected to the output side of source II. A second respective external electrode I3, associated with each tube, is grounded, completing the excitation field circuit. Grounded electrodes I3 may be entirely eliminated, the grounding of the internal electrodes and the external circuitry being used to complete the excitation circuit. Furthermore, a single'electrode I2 may be employed for establishing the stabilizing field for a plurality of properly grouped tubes.

Fig. 2 illustrates a modified embodiment of the above-described trigger circuit, Those elements in Figs. 1 and 2 which are identified by the same reference numerals are identical both structurally and operatively. The circuit in Fig. 2 employs two gas triodes ZI and 22 in place of the diodes I and 2 shown in Fig. 1. The grids of gas tubes 2i and 22 in Fig. 2 are connected to a source I l of variable D. C, voltage. By varying the value of source I4, the breakdown potential of tubes 2| and 22 may be regulated with negligible effect upon their extinction level, a fact well known in the art. Therefore, varying the value of source I4 will vary the range, in each tube, between its breakdown and extinction levels, allowing regulation of that range for optimum operating conditions. In the description of Fig. 1, it was noted that the. grounded external excitation electrodes I3 could be omitted without impairing circuit operation. Such an arrange ment is illustrated in Fig. 2.

It will be apparent that either trigger circuit described above may be used in an ordinary binary counting circuit by connecting anapproe priate number of such trigger circuits in series and feeding to each trigger circuit, tripping pulses which are tapped from the high potential electrode of either tube in the preceding circuit. By, observing which tube in each circuit is conducting, it may be readily ascertained how many tripping pulses have been introduced into the system.

It will also be noted that the formed pulses appearing at either tube plate may be coupled, in a suitable manner, into any desired utilization circuit I0 (Figs. 1 and 2), as well as into succeeding trigger circuit stages. Furthermore, it will be obvious to one skilled in the art that the output pulses may be isolated from the input pulses by tapping the former from across a suitable cathode resistor associated with either tube.

It will appear further, that either of the foregoing circuits may be triggered by negative as Upon receipt of a negative pulse, the plate potentials of both tubes drop an equal amount and the conducting tube is extinguished, its potential level rising to 3+ due to the decreased drop across its plate resistor 4 or 5.

the other tube through coupling resistor 9, raising it above its breakdown level and firingit. The circuit values are such that the rise of the non-conducting tube to breakdown level is smaller than the rise of the conducting tube to 3+ when it is extinguished. Thus, the rise of the extinguished tube is of sufiicient magnitude to raise That rise in potential is fed'to' the ot er it."

tu ov fiSi Qe Q W is! a are,

oscillator the followin thetube-{l or 2, having the lower breakdc ivn potential will fire first. Again, for'purposes of illustration, it may be assumed that tube I has the lower breakdown potential. fires, its plate potential drops and a negative pulse is fed throughcoupling condenser 9 and im-"f'i pressed upon tube 2,: preventing tube "2 from' tion circuit I), may be varied by varying the time constant of the'circuit comprising the resistor 4 or 5 associated with the'non-conducting tube and condenser 9'.

Univibrator action pulses includes the previously described extinction of the normally conducting tube, the conse-' quent firing of the "other tube, and the subsequent restoration of the circuit to its rest condition. I I claimi ls-A stabilized pulse generating trigger circuit comprising a pair of gas-filled tubes, each tube having two internal electrodes, a respective-con nection from one electrode of each of said tubes to ground, a respective discharge resistor connecting the ungrounded electrode of each of said tubes to the positive terminal-of a source of unifiring'under the influence oi the 13+ voltages" At the timef'ofi the negative Surge acrosscon denser 9, both sides of that condenser are lowered to the operating potential of tube I, The left side (in thedrawing) of that condenser remains at'suchoperating level as long as tube I continues to conduct. However, the right side of condenser 9,-connected to and therefore at the potential of tube 2, is recharged toward'B+ level through resistor 5 in an amount or time deter mined by the time constant of the circuit com prising resistor 5 and condenser 9.

Since B+ is, in an oscillator, at 'a higher 'po-' tential than'the breakdown level for either tube I or 2, tube 2 fires beforeit has returned to 13-] level. 'Thereupon, the potential'dropacross re sistor 5 causes the plate potential of tube '2 to drop, coupling a negative pulse through condenser 9 to tube I andextinguishing that tube in the manner previously described. Each tube in turn will continue to fire in this manner. The circuit will thereby function as; afree running oscillator.

It will be remembered that the recovery time for either tube, i. e., the time'required for a tube to rise from the level at which it was extinguished to its breakdown level, is determined by the time constant of the circuit consisting of the respective associated resistor 4 or 5 and the coupling condenser 9. Therefore, the recovery time; and consequently the frequency of oscillation, may be varied by varying the value of condenser 9.

Operation as a univibmtor As a further example of the general utility of the circuits illustrated in Figs. 1 and 2, either of these circuits may be used as aone-shot multivibrator or univibrator.

For thispurpose, the tapped positive potential from source 3 to one tube of a circuit must be greater than the breakdown potential of that tube. On the other hand, the potential tapped from source 3 to the other tube of the circuit must be between breakdown level and extinction level for that tube. Therefore, the first of such tubes is normally conducting and the second is normally non-conducting. A positive tripping pulse from source 6 fires the non-conducting tube and extinguishes its companion in the manner described under trigger circuit operation. Recharging of the coupling condenser 9 through the associated discharge circuit resistor 4 or 5 restores the normally conducting tube to conduction. The consequent negative surge across condenser 9 thereupon extinguishes the normally non-conducting tube. It will be apparent that the width of the output pulse, fed to the utilizadirectional potential, the potential of said terminal being less than the breakdown potential and greater than the ionization potential of either of I said tubes, whereby said trigger circuit is maintained in a fixed condition of operation when either of said tubes is conducting and itscompanion tube is non-conducting, means for firing said non-conducting tube, means responsive to said firing of the last mentioned tube for extinguishing the other tube, excitation means including, .at least one electrode external of and adjacent to said tubes, and a source of audio or higher frequency potential coupled to the external electrode for applying to the'gas within said tubes an excitation field of a potential level sufl'icient to stabilize the characteristics of the tubes but in sufiicient to sustain conduction be tween said internal electrodes.

2. A stabilized pulse generating trigger circuit comprising a pairof gasefilled tubes, each having at least a cathode, an anode, and a grid, means for biasing the grid of each of said tubesto establish a predetermined breakdown potential for that tube, a respective. connectionfrom the oathode of, each of said tubes to ground, a respective discharge resistor connecting the anode of each of said tubes to the positive terminal of a source of unidirectional potential, the potential of said terminal being less than the breakdown potential and greater than the ionization potential of either tube, whereby said trigger circuit is maintained in a fixed condition of operation when either of said tubes is conducting and its companion tube is non-conducting, means for firing said non-conducting tube, means responsive to said firing of the last mentioned tube for extinguishing the other tube, excitation means including, at least one electrode external of and adjacent to said tubes, and a source of audio or higher frequency potential coupled to the external electrode for applying to the gas within said tubes an excitation field of a potential level suflicient to stabilize the characteristics of the tubes but insuflicient to sustain conduction between the cathode and anode of either tube.

3. A stabilized pulse generator circuit comprising a pair of gas-filled tubes, each having two internal electrodes, a respective connection from one electrode of each of said tubes to ground, a

resistor connecting the remaining electrode of a first one of said tubes to the positive terminal of a source of unidirectional potential, the potential of said terminal being greater than the breakdown potentials of said tubes, whereby said first tube is caused to conduct, and means including a resistor connecting the ungrounded electrode of the second tube to the positive termiwith negative 1 tripping nalof said source for .ca usingathe second'tubea to conduct to thereby produce "a negative surge at the ungrounded electrode of the second tube, -.-a; condenser mutually connecting the respectiveungrounded electrodes of the first andsecond tubes to couple saidnegativesurge to "said ungrounded electrode of the first tube "forextinguishing said first tube,- whereby -;said first and second tubes conduct alternately at least one electrode external of and adjacent to said tubes, at source of audio or higher frequency excitation potential coupled to theexternal electrode-for applying to they gaswithin said tubes an excitation field of a potential level suflicient tostabilize the characteristics of said tubes and insufficient to sustain conduction between saidinternal elec-i trodes, and a utilization circuit coupled stoma principal electrode ofeither of said tubes for de-.

riving pulses from said pulse generatingicircuita 4.. A stabilized pulsegenerator. circuit c0mprising a pair of gas-filled tubes, each having atleast a cathode, an anodeand a grid, eharacterizedby, means forbiasing the grid-of each of said tubes to establish a predetermined breakdown potential for said tubes, a respective connection fromthe cathode of eachof said tubes to groundja resistor connecting the anodeof a first one-of saidtubes to thepositive terminal of a source of unidirectional potential, the potential of said terminal being greater than the breakdown potentials. of

saidtubes, whereby said first tube is, caused toconduct, with means including a resistor con necting the anode of the second tube to said positive terminal for causing said second tube to conduct to thereby. produce a negative surge at the anode of the second tube, a condenser mutually connecting the.respective anodes ,of the first and second tubes to couple said negativesurge to said anode of the first tube for extinguishing said firstftube, whereby said first ,and second tubes conduct alte'rnatelxat least one electrode external of'and adjacent to said tubes, a source of audio or higher frequency excitation potential coupled to theexternal electrode fora pplying -tothe gas within said tubes. an excitationcfield of a potential level sufficient. to stabilize the charac j teristics of said tubes and insufiicientto sustain conduction between the cathode and anode of eithertube, and a utilizationcircuit coupledto ,a principal electrode of either of said tubes for de- 5- riving pulses from said pulse generating circuit.

5. In a circuit'employinga gas-filled tube including at least twointernal electrodes, means for stabilizing the characteristics of said-tube, said means comprising at least one -electrode ex-- ternal of and adjacent to said tube, and a source,v of audio or higher frequency excitation potential coupled to the external electrodefor applying to the gas within said tube an excitationfield ofa potential level sufificient' to stabilize the: characteristics of said tubes and insufiicient to internal elec-r sustain conduction between saidtrodes. V,

6. A stabilized pulse generating circuit -comjacent to said tubes, a source of audio or higher frequency excitationpotential coupled to theexternal electrode for applying to the gas within said tubes an excitation field of a potential level sufiicient to stabilize the characteristics of said tubes and insufficient to sustain conduction between the cathode andanode of either tube,and a utilization circuit coupled to a principal electrode of either of :said tubes for deriving pulses from said pulse generating circuit. I MERYL C. BURNS-.- I

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Date Number v Name 2,017,112 Wehnert a. Oct. 15, 1935 2,116,719 Wehnert May 10, 1938- 2,348,555 Mathes May 9, 1944 2,359,747 C'arleton Oct. 10, 1944' 2,365,567

Langer Dec. 19, 1944 

